LEARN / GLOSSARY
Nameplate capacity
The maximum theoretical output of a generator as reported to EIA by its manufacturer or operator. A design rating rather than a measurement, and larger than the figure EIA actually publishes.
Definition
Nameplate capacity is the maximum theoretical output of a generator, expressed in megawatts, as reported to the Energy Information Administration by the manufacturer or operator. The figure is a design rating registered with authorities rather than a measurement of what the unit delivers.
Why the dictionary version is insufficient
Treating nameplate capacity as the amount of power a plant supplies overstates in every case and overstates unevenly across technologies. EIA publishes three separate capacity figures for this reason: nameplate capacity, net summer capacity and net winter capacity, which differ because the temperature of generator cooling fluid changes with the season.
Measurement noteEIA reports generating capacity as net summer capacity in most of its electricity data products, not as nameplate. Net summer capacity is the maximum output the equipment can supply to system load as demonstrated in a multi-hour test at the time of summer peak demand. Two figures for the same plant, both correct, differing by whichever basis was used.
Why it matters for capacity
Announcements of new generation are usually stated in nameplate terms because that is the larger number. Comparing an announced nameplate figure against a system need expressed in net summer capacity compares two different quantities, and the error runs in the direction of understating what still has to be built.
Related terms
Capacity factor · Capacity utilization · Firm power
Appears in
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Read next
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Sources
- U.S. Energy Information Administration, Electricity generation, capacity, and sales in the United States. eia.gov